Saliva provides protection against caries in several ways. First, it acts as a buffer by neutralizing much of the acids produced by plaque biofilm as a result of carbohydrate metabolism. Second, normal saliva contains bicarbonate, phosphate, and protein that dilute and neutralize acids to maintain oral pH. A neutral pH is around 7. Therefore, after an acidic drink is consumed, the pH of the oral cavity is rapidly normalized by the components of saliva. However, if the frequency or duration of the acidic drink is extended, it becomes more difficult for saliva to buffer the continuous supply of acid and no longer offers caries protection. Because saliva is saturated with calcium, phosphate, and fluoride ions, the potential for remineralization (restoration of damaged enamel) and resistance to enamel dissolution exists. Finally, antimicrobial elements in saliva, such as immunoglobulin IgA, either interfere with adherence of bacteria or compete with bacteria to attach to the tooth surface. An alkaline saliva offers protection, whereas an acidic saliva increases susceptibility to caries.
The pH of diet and regular soft drinks, bottled iced teas, and sports drinks ranges from 2.5 to 3.5.